The visible light communication is an emerging short-distance high-speed wireless optical communication technology developed based on the light emitting diode (LED) technology. The most important feature of the visible light communication is that it meets the demand for normal lighting while supporting the communication and it is green and environmental friendly and has no electromagnetic interference. With the development of the visible light communication, a visible light communication MIMO system has also become one of the hotspot technologies.
The requirement on the basic structure of the visible light communication MIMO system is: designing a transmitter into an LED array structure, and requiring that the luminous intensity meets the indoor lighting requirements (500l×); and designing a receiver into a two-dimensional array multi-point detection structure. The visible light communication MIMO system converts the disadvantage of “multipath effect” caused by the multiple reflections of the light ray in the space into an advantage, which exponentially improves the system throughput and the data transmission rate with the spatial multiplexing technology, and also effectively reduces the influence of intersymbol interference with the array sending technology. Thus it can be seen that, the MIMO system is extremely applicable to a diffused channel of the visible light communication, and it reduces the sensibility of a mobile terminal to the jitter of the optical channel, which can enhance the signal received ability and improve the channel utilization rate in the cases of the location change of the terminal, the channel sudden change and the jitter and so on.
The application of the MIMO system mainly has three hotspot technologies in the visible light communication: one is the spatial diversity, that is, at both a sending end and a receiving end, the data are transmitted in a form of array to reduce the bit error caused by the delay and improve the channel reliability; another one is the spatial multiplexing, that is, at the sending end, the data are transmitted by means of layered space-time multiplexing (BLAST), which can exponentially improve the system throughput and the data transmission rate; and still another one is the beamforming, that is, it is to make the channel directivity precise by reducing the field of view of the light source, thereby reducing the channel interference (ICI) between the adjacent light sources.
At present, in the visible light communication MIMO system, when jitter occurs in the mobile terminal, a distortion will occur in the data of the sending end, thereby causing receiving and sending frames asynchronously; and the optical channel received by the receiver will be forced to interrupt, thus the communication cannot be continued. Therefore, when a long string of locating information is continuously transmitted, the information loss will also be caused due to the occurred jitter, which reduces the data transmission efficiency.